Display screen or portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or portion thereof with agraphical user interface showing our new design.

The outermost broken line rectangle shows the display screen or portionthereof. All other broken lines show portions of the graphical userinterface and form no part of the claimed design.

CLAIM The ornamental design for a display screen or portion thereof witha graphical user interface, as shown and described.